SOIL HEALTH AND EROSION

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1 SOIL HEALTH AND EROSION (Taken from Appendix F of the Tualatin Soil and Water Conservation District s Long Range Business Plan for 2011-) Description of Resource Concern Healthy soil gives us clean air and water, bountiful crops and forests, productive pastures, diverse wildlife, and beautiful landscapes. In basic terms, soil health is the capacity of a soil to function. It s a measure of how well a soil is able to: sustain plant and animal productivity and diversity, maintain and enhance water and air quality, and support human health and the surrounding environment. Enhancing organic matter, preventing erosion, and avoiding soil compaction are three key components to maintaining healthy soil. Organic Matter Organic matter is material in soil which is derived from once-living organisms. Adding organic matter improves soil structure, enhances water and nutrient holding capacity, protects soil from erosion and compaction, and supports a healthy community of organisms. Soil is full of a diversity of living organisms, each important to the overall health of the soil. More individual organisms exist in a teaspoon of soil than there are people on Earth! The soil food web (below, Figure 1) is the community of organisms living all or part of their lives in the soil. The arrows represent conversions of nutrients and energy as one organism eats another. A suitable habitat for these organisms must be maintained in order to manage healthy soil. The Soil Conditioning Index (SCI) is a tool used by the Natural Resources Conservation Service and local soil and water conservation districts to estimate whether or not soil organic matter levels will increase after a conservation practice is implemented. Examples of conservation practices that increase soil organic matter include reduced tillage 1, crop rotations 2, and cover crops 3. The tool predicts the amount of organic material returned to or removed from the soil, the decomposition of organic matter due to tillage or other field operations, and the effect of soil erosion associated with the management system. A positive SCI number indicates an increase in organic matter, while a negative SCI number indicates a decrease in organic matter in the soil. The Willamette Valley Soil Quality Card was developed by farmers in collaboration with local soil and water conservation districts, the Natural Resources Conservation Service and Oregon State University to assess current soil quality condition throughout the Willamette Valley. The tool allows farmers or gardeners to record changes in soil quality to compare different fields and management practices. 1 Reduced tillage is a practice of minimizing soil erosion and leaving crop residue or stubble on the ground. 2 Crop rotation is the successive planting of different crops on the same land to improve soil health. 3 Cover crops are grasses, grains, or legumes planted after harvest to hold the soil and improve soil health. Cover crops can also be planted between rows in an orchard to prevent bare soil.

2 Figure 1. The Soil Food Web ( Soil erosion At a most basic level, the problem with erosion is things move to places they should not be. In most cases, things refers to soil, bacteria, chemicals, and nutrients. The places they should not be refers mainly to water bodies used for drinking water, fish and wildlife habitat, irrigation, and recreation. Several types of erosion harm the natural resources of the Tualatin River Watershed: sheet and rill erosion, gully erosion, and streambank erosion. Sheet and rill erosion is caused by water, usually from raindrops or melted snow, flowing over the ground as a shallow sheet about While the farmer holds the title to the land, actually it belongs to all the people because civilization itself rests upon the soil. --THOMAS JEFFERSON the thickness of a dime. As it moves, the water picks up tiny particles of soil and whatever else might be on the soil, such as bacteria or chemicals. If the ground is irregular, full of bumps and dips, the sheet of water doesn t go far before it settles into the lower spots. Once it does, the water continues to push forward causing little grooves, or rills, to form in the soil. These rills are tiny, well-defined ditches no more than a few inches deep. The water can gain strength and speed to lengthen these little trenches, picking up more particles along the way. Eventually, these could connect with rivers or streams and contaminate them with whatever bacteria, nutrients, or chemicals they carry.

3 Gully erosion is similar to rill erosion, but the size of the rut is much larger: about one-foot deep by one-foot wide. Obviously, a groove this size carries more water and more particles of eroded soil. Streambank erosion is a problem in stream channels and flood-prone areas. here there are not enough grasses, plants, and trees next to streams, there is little to stop water and contaminates from flowing right in. Grasses, plants, and trees are important because they soak up many pollutants before they reach the stream. Roots also stabilize soil on the streambanks, keeping it from eroding or sloughing into the water. Why Worry about Erosion? Erosion affects every resident in the Tualatin River Watershed. It has an impact on the water we drink, the food we eat, and the recreation we seek. Because erosion washes potentially harmful elements into our rivers and streams, we need to be concerned about the quality of our drinking water. In order to make sure water is safe to drink, it must go through various cleaning processes, which water users pay for. The more cleaning and testing necessary, the more expensive the treatment will be. Erosion also decreases the recreational and aesthetic value of our waterways. Many people in the Tualatin River Watershed find great pleasure in the beauty of nature surrounding us. Erosion, and the pollution it may cause, could make our waterways unsafe for swimming and fishing. Even if we do fish, we may have a hard time catching anything because erosion also hurts fish. Eroded soil containing nitrogen, phosphorus, and organic matter is carried into water. These nutrients trigger algal blooms that make water murky and use up oxygen. Streambank erosion also destroys fish habitat. Sediment 4 covers fish spawning and rearing areas. In addition to soil settling in important fish habitat, eroded soil and nutrients can fill up roadside ditches and drainage areas. Residents must pay the expense to keep ditches cleaned out so they function properly. Topsoil We have given examples of problems when soil particles are moved to someplace they don t belong, but what about moving soil from the places it does belong? The most valuable nutrients are in the top layer of the ground. When water runs over topsoil, it can carry it away. When crops are planted there, they don t have the nutrients and nourishment from the topsoil needed to grow. As a result, more fertilizers must be added to the soil. Lack of topsoil may result in lower quality crops and the food they produce. Over time, erosion makes soil less productive. Soil erosion is happening on a wide range of lands in the Tualatin River Watershed. On agriculture land, erosion decreases productivity. Farmers spend time and money to meet regulations, which get tougher when conditions do not improve. In urban areas, development, construction, excavation, and clearing cause erosion. Property owners, contractors, and engineers face strict permit requirements, increased risk of flooding, and additional fees for construction. The bottom line is soil erosion costs every resident of the Tualatin River Watershed, whether with time, money, opportunity, or piece of mind. If the problem does not improve, expenses to treat water for human use and to clean up water to meet state and federal standards will increase. Erosion may impair residents quality of life. It could cause a decrease in the condition of food and water, degrade wildlife habitat, add costs and regulations for agriculture producers, and suppress the aesthetic and recreational value of our rivers. If the conditions cannot be improved with local efforts, state and federal agencies will invoke further regulation. 4 Sediment Finely divided solid material that settles to the bottom of water.

4 Figure 1. Left: Turbidity has stirred-up sediment to make the water murky. Right: Gully erosion through a farmer s field. Soil Compaction A third measure of soil health is one you may be able to determine with your eyes closed and your hands behind your back: soil compaction. If soil is compacted, it will feel hard and likely have clods you can t easily break. Healthy soil should feel soft and spongy, sinking a little under your weight. Good quality soil is porous, meaning it has air spaces that make it give beneath your feet. These air pockets are essential for water and nutrients to move throughout the soil. Soft, loose soil also allows plant roots to spread out and take in water and nutrients to grow. When soil is solid and hard, water cannot soak in. Instead, water runs over the surface causing erosion. Soil can be compacted by mechanical, animal, or natural causes. Imagine a gardener s shock at seeing a tractor drive repeatedly over a backyard vegetable garden! Yet seeing a tractor on a farmer s field would hardly be cause for alarm. With heavy machinery frequently driving over its surface, soil is sure to be compacted. Compaction from equipment traffic is inevitable; however the damage can be reduced. Tractors should avoid moist soil, since wet soils tend to compact more easily. Farmers can reduce compacted area by confining traffic to the same wheel tracks and choosing tires appropriate for the soil characteristics. Farm equipment is not the only kind of traffic to cause compaction; animal traffic is also to blame. When hoofs carrying thousands of pounds continuously plod over the ground, it s easy to see how the soil could become dense. Natural consolidation also causes compaction. This is due to soil structure and its chemical and biological properties. Over time, elements in the soil, such as organic matter, break down and condense naturally. Without the soil, there would be no us. In return, we must recognize that the soils that support our lives cannot be taken for granted; they must be nurtured. --Neil Sampson, from The Living Soil, essay for the 2004 National Soil Stewardship week. As mentioned earlier, one of the most serious problems from soil compaction is its effect on plant and crop production. When soil quality is reduced, crop quality suffers. Also, because the ground is so solid, water cannot soak in as quickly. Water may

5 run over the surface of the soil resulting in erosion that negatively affects crops and water quality. At the same time, water use efficiency is reduced as irrigated water is not able to penetrate the soil. Agriculture producers must cover the cost for this lack of efficiency. It could cost them in other ways too, since fertilizer efficiency is reduced and compacted soils require more horsepower (fuel) to cultivate. Soil compaction has been a long-standing concern for all agriculture landowners in Washington County. Strategies exist to address the concerns, but more research must be done for cost-effective practices to avoid compaction. We need to explore both preventive measures and strategies to correct compacted soils. If appropriate measures are not taken, productivity on some farms will decline. Prime farmland could be converted to uses not capable of growing food crops. Building organic matter, controlling erosion, and preventing soil compaction do not guarantee good soil quality, but they help to improve and protect soil quality and productivity. Highlights of Accomplishments General public recognition of this problem came only in 1930, when H. H. Bennett and associates recognized the damage being done and obtained federal support for erosion control efforts." (The Nature and Properties of Soils, Nyle C. Brady, 1990, page 432) When the District formed in 1955, it integrated resource concerns that specifically addressed soil erosion, water quality, and loss of soil productivity in its long-range plan. In 1988, the Tualatin River Watershed Agricultural Non-point Source Water Quality Plan identified surface water quality resource concerns and the impacts on water quality. Trends toward addressing and controlling soil erosion show improvement through implementing Best Management Practices. There have also been advancements in technology to help control erosion, which include seeding fall crops with less (or no) tillage 5, use of cover crops 6, underground outlets, filter strips 7, grassed waterways 8, flow diversions, terraces 9, and improved nutrient management 10. Additional support through accelerated federal, state, and local efforts, and a coordinated effort amongst conservation partners, has also assisted with the trends. For example, projects were completed along Dairy and McKay Creek through USDA Dairy McKay Creek Hydrologic Unit Area funding from Data show a slow but steady improvement in surface water quality in the Tualatin River Watershed. 5 Tillage The mechanical manipulation of soil for any purpose. In agriculture it is usually restricted to modifying soil conditions for crop production. 6 Cover Crop A close-growing crop grown primarily to protect and improve soil between periods of regular crop production or between trees and vines in orchards and vineyards. 7 Filter Strip A strip or area of herbaceous vegetation situated between cropland, grazing land, disturbed land (including forest land), and environmentally sensitive areas. 8 Grassed Waterway A natural or constructed channel shaped or graded to required dimensions and established with suitable vegetation. 9 Terrace A narrow, flat stretch of ground, often having a steep slope facing a river or sea. 10 Nutrient Management Utilizing soil testing to determine how much fertilizer or organic matter to apply.

6 During the past five years, conservation practices have been implemented to address soil erosion and soil health concerns. These include, but are not limited to, the above listed Best Management Practices. These practices help reduce soil erosion, increase organic matter, reduce compaction, and improve overall soil health. Desired Conditions Soil Conditioning Index is a positive value 11. Indicators on the Willamette Valley Soil Quality Card are above a 5 rating Soil productivity is at its highest potential. Water is allowed to infiltrate the soil, instead of causing runoff and erosion. The soil stores water for future plant uptake and recharges the underground water table 13. Effective and economically feasible methods are available to landowners to prevent soil compaction and remediate soils degraded by compaction. Mechanically compacted soils are renovated sufficiently to restore plant root growth and/or water movement. Landowners work the fields when the soil moisture level is not too wet; use tillage equipment to break up clods; incorporate organic matter into the soil; kill weeds; and create a more favorable seedbed. Animals are fenced out of wet areas. No visible streambank erosion. No fields get washed away. All highly erodible land is cropped in such a fashion there is little if any chance of erosion. Ditches manage maximum flow without overflowing the banks and causing erosion. A healthy stream has vegetation growing on both sides of the stream for its entire reach. Vegetation absorbs the energy of falling rain and melting snow, lessening soil displacement. Vegetation slows the velocity of runoff and acts as a filter to catch eroding soil and contaminants. Plant roots and grasses hold soil particles in place. No streams have scouring at the bends. Goals By the end of, demonstrate an improvement in: Soil Conditioning Index for those farms with active conservation plans Number of farms utilizing the Willamette Valley Soil Quality Card A positive SCI value means the level of organic matter is predicted to increase under the management system. 12 The Willamette Valley Soil Quality Card was developed by local SWCDs, NRCS and OSU to assess current soil quality condition throughout the Willamette Valley. 13 Water Table The level below the soil surface that is saturated with water.

7 Strategies and Actions Table 1. Timeline of Desired Conditions and Actions for Soil Health and Erosion. Benchmark Timeline Actions Assessing soil quality and calculating the Soil Conditioning Index Informed farmers and public about the importance of maintaining soil health Dec Dec Develop conservation plans Dec Status reviews Dec Focus on field erosion caused by general farming practices with an emphasis on nurseries and Christmas tree farms during the first year Calculate the SCI on fields with current conservation plans and advise these farmers on what the results are and which practices to implement Encourage farmers to utilize the Willamette Valley Soil Quality Card to assess their soil quality General soil health program used to educate farmers and the public Provide information to farmers on how to assess their soil quality Add soil health concerns in all conservation plans Monitor whether planned practices were implemented to improve soil health and erosion (cover crops, conservation cover, nutrient management, residue management) Key partners necessary to achieve the desired conditions include: Natural Resources Conservation Service Oregon Association of Nurseries (OAN) Oregon Department of Agriculture (Water Quality Specialist focused on nurseries and Christmas trees) Christmas tree growers Nursery growers Measurements Improvements in soil test results Number of farmers who have used the Soil Conditioning Index Soil condition index improvements Number of farmers who have used the Willamette Valley Soil Quality Card